The present invention consists of a portable system for the "breath by breath" measurement of the metabolic parameters of an individual, with telemetric data transmission and storage of results for further analysis.
It is known that, nowadays, the analysis of the metabolic response of an individual is usually performed in laboratories using stationary equipment able to measure mainly the following parameters: oxygen uptake (VO.sub.2), carbon dioxide production (VCO.sub.2), respiratory quotient (RQ=VCO.sub.2 /VO.sub.2), ventilation (VE) and heart rate (HR).
These equipments allow testing to occur, with the use of an ergometer, while the individual performs a physical activity, such as cycling or using a treadmill.
The major limitation of the previously mentioned methodology is related to the fact that most of the activities (sports and non-sports) such as skiing, tennis, the daily job, or driving a wheelchair, cannot be correctly simulated in the lab.
Up to some years ago, portable systems for metabolic tests were not available. The device described in the U.S. Pat. No. 4,658,832 (BRUGNOLI), dated Apr. 21, 1987, was the first system with limited dimensions introduced into the market.
During the last years, however, the measurement techniques of the metabolic parameters used by the stationary systems has evolved, turning from the "mixing chamber" methodology to the "breath by breath" technique.
The first one, as it is well known, provides the results as an average of all the breaths carried out in a consistent time interval (typically 30 seconds), while the second one provides results for each breath of the individual.
The "breath by breath" analysis is described in detail in the following publications:
Beaver, Wasserman, Whipp, JAP. 34(1): 128-132, 1973 "On Line Computer Analysis and Breath by Breath Graphical Display of Exercise Function Tests"; PA0 Sue, Hansen, Blais, Wasserman, JAP, 49(3): 456-461, 1980: "Measurement and Analysis of Gas Exchange, Using a Programmable Calculator"; PA0 Wasserman et al. 1994: "Principles of Exercise Testing and Interpretation", 2.sup.nd Edition. PA0 it does not allow the detection of fast variations of the metabolic functions following sudden changes in the workload; PA0 it does not allow for the analysis of the gas exchange corresponding to each breath, but only related to the average of several breaths; and PA0 it does not allow the measurement of some important parameters such as FetCO.sub.2 or VD/Vt.
The origin of the two previously mentioned techniques is related to a technological limitation: the measurement of the oxygen uptake (VO.sub.2) and carbon dioxide production (VCO.sub.2) in correspondence of each breath, requires the use of two gas analyzers with a response time lower than 200 milliseconds. When such analyzers are not available, it is possible to mix the expired air in a "mixing chamber" in order to average the concentrations of the two gases (O.sub.2 and CO.sub.2) making the fluctuations too slow to be accurately detected by the slow response time analyzers.
The "mixing chamber" analysis has however some great limitations:
Nowadays, although some portable systems for the measurements of metabolic parameters in real conditions are already available, none of those is able to provide measurements with the "breath by breath" technique.
The main reason for this lack is that oxygen analyzers with a fast response time (tr&lt;200 msec) with dimensions and power consumption compatible with the requirements of a portable system are not available.